One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,5,3)(4,7,8,6)(9,10,14,16)(11,15,19,22)(12,17,21,24)(13,20,23,18)(26,31)(27,33)(32,38)(34,39)(2,3)(6,7)(9,11)(10,15)(12,18)(13,17)(14,19)(16,22)(20,21)(23,24)(25,26)(27,28)(29,32)(30,31)(33,35)(34,36)(37,38)(39,40) involution — undirected(1,3,5,2)(4,7,8,6)(10,16)(11,19)(12,21)(13,23)(27,33)(28,35)(29,37)(32,38)(1,4)(2,6)(3,7)(5,8)(9,11)(10,15)(12,18)(13,17)(14,19)(16,22)(20,21)(23,24)(25,27,30,33)(26,28,31,35)(29,34,37,39)(32,36,38,40)(9,12)(10,17)(11,20)(13,22)(14,21)(15,23)(16,24)(18,19)(25,28)(26,27)(29,36)(30,35)(31,33)(32,34)(37,40)(38,39) involution — undirected(9,13,14,23)(10,18,16,20)(11,17,19,24)(12,22,21,15)(25,29)(26,32)(27,34)(28,36)(30,37)(31,38)(33,39)(35,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.